A little more info on it.
I would suspect a major leak.
#1 Freon is non consumable, if it's not there then there is a leak
#2 A/C is a delicate balance between liquid/gas (low side/high side) and too much freon is just as bad as not enough
#3 If you are not prepaired to buy a set of A/C gauges, and be willing to possibly buy a vaccum pump or a/c die and replace the proper componets, then don't even waste your time.
#4 90% of the time your going to have to pull a vaccum, flush the lines and most the time replace the accumilator and the Oriface tube/expansion valve.
#5 The only easy fix is if one of the pressure switches is bad, there is no just add freon fixes.
#6 Please Please don't just add freon w/ a charging kit because you think it needs it, It doesn't work like that.
#7 These guys are a execlent source for help and if you listen to the procedures as you are told you will end up w/ some ice cold A/C, being hard headed is expensive.
http://www.autoacforum.com/
#8 And here is a link from AC kits.com to what a person needs to recharge a air conditioning.
A/C starter Kit
#9 Adding freon to a system that has a good charge can be dangerous and can cause you harm, if the pressures get to high and blow the freon can or something in the system.